3,619 research outputs found
Comment on "Consistency, amplitudes, and probabilities in quantum theory"
In a recent article [Phys. Rev. A 57, 1572 (1998)] Caticha has concluded that
``nonlinear variants of quantum mechanics are inconsistent.'' In this note we
identify what it is that nonlinear quantum theories have been shown to be
inconsistent with.Comment: LaTeX, 5 pages, no figure
Strongly disordered TiN and NbTiN s-wave superconductors probed by microwave electrodynamics
We probe the effects of strong disorder (2.4 < kFl < 8.6) on
superconductivity in thin films of niobium titanium nitride and titanium
nitride by measuring the microwave electrodynamics in coplanar waveguide
resonators. We find a gradual evolution of the electromagnetic response with
disorder, deviating from Mattis-Bardeen theory, for both materials. This result
can be understood as due to changes in the quasiparticle density of states,
induced by the short elastic scattering length. The observations are consistent
with a model using an effective pair breaker, dependent on the level of
disorder.Comment: 5+4 pages, 3 + 2 figure
Weak Localization Effect in Superconductors
We study the effect of weak localization on the transition temperatures of
superconductors using time-reversed scattered state pairs, and find that the
weak localization effect weakens electron-phonon interactions. With solving the
BCS equation, the calculated values for are in good agreement
with experimental data for various two- and three-dimensional disordered
superconductors. We also find that the critical sheet resistance for the
suppression of superconductivity in thin films does not satisfy the universal
behavior but depends on sample, in good agreement with experiments. but depends
on sample, in good agreement with experiments.Comment: 14 pages, Revtex, 5 ps figure
Magnetic fluctuations in 2D metals close to the Stoner instability
We consider the effect of potential disorder on magnetic properties of a
two-dimensional metallic system (with conductance ) when interaction in
the triplet channel is so strong that the system is close to the threshold of
the Stoner instability. We show, that under these conditions there is an
exponentially small probability for the system to form local spin droplets
which are local regions with non zero spin density. Using a non-local version
of the optimal fluctuation method we find analytically the probability
distribution and the typical spin of a local spin droplet (LSD). In particular,
we show that both the probability to form a LSD and its typical spin are
independent of the size of the droplet (within the exponential accuracy). The
LSDs manifest themselves in temperature dependence of observable quantities. We
show, that below certain cross-over temperature the paramagnetic susceptibility
acquires the Curie-like temperature dependence, while the dephasing time
(extracted from magneto-resistance measurements) saturates.Comment: 15 pages, 4 figure
Simplicial quantum dynamics
Present-day quantum field theory can be regularized by a decomposition into
quantum simplices. This replaces the infinite-dimensional Hilbert space by a
high-dimensional spinor space and singular canonical Lie groups by regular spin
groups. It radically changes the uncertainty principle for small distances.
Gaugeons, including the gravitational, are represented as bound fermion-pairs,
and space-time curvature as a singular organized limit of quantum
non-commutativity.
Keywords: Quantum logic, quantum set theory, quantum gravity, quantum
topology, simplicial quantization.Comment: 25 pages. 1 table. Conference of the International Association for
Relativistic Dynamics, Taiwan, 201
Disordered electron liquid in double quantum well heterostructures: Renormalization group analysis and dephasing rate
We report a detailed study of the influence of the electron-electron
interaction on physical observables (conductance, etc.) of a disordered
electron liquid in double quantum well heterostructure. We find that even in
the case of common elastic scattering off electrons in both quantum wells, the
asymmetry in the electron-electron interaction across and within quantum wells
decouples them at low temperatures. Our results are in quantitative agreement
with recent transport experiments on the gated double quantum well
AlGaAs/GaAs/AlGaAs heterostructures.Comment: 15 pages; 5 figure
Charged mobile complexes in magnetic fields: A novel selection rule for magneto-optical transitions
The implications of magnetic translations for internal optical transitions of
charged mobile electron-hole (--) complexes and ions in a uniform
magnetic field are discussed. It is shown that transitions of such
complexes are governed by a novel exact selection rule. Internal intraband
transitions of two-dimensional (2D) charged excitons in strong magnetic
fields are considered as an illustrative example.Comment: 4 pages, 2 figure
Clifford algebra as quantum language
We suggest Clifford algebra as a useful simplifying language for present
quantum dynamics. Clifford algebras arise from representations of the
permutation groups as they arise from representations of the rotation groups.
Aggregates using such representations for their permutations obey Clifford
statistics. The vectors supporting the Clifford algebras of permutations and
rotations are plexors and spinors respectively. Physical spinors may actually
be plexors describing quantum ensembles, not simple individuals. We use
Clifford statistics to define quantum fields on a quantum space-time, and to
formulate a quantum dynamics-field-space-time unity that evades the
compactification problem. The quantum bits of history regarded as a quantum
computation seem to obey a Clifford statistics.Comment: 13 pages, no figures. Some of these results were presented at the
American Physical Society Centennial Meeting, Atlanta, March 25, 199
Effects and Propositions
The quantum logical and quantum information-theoretic traditions have exerted
an especially powerful influence on Bub's thinking about the conceptual
foundations of quantum mechanics. This paper discusses both the quantum logical
and information-theoretic traditions from the point of view of their
representational frameworks. I argue that it is at this level, at the level of
its framework, that the quantum logical tradition has retained its centrality
to Bub's thought. It is further argued that there is implicit in the quantum
information-theoretic tradition a set of ideas that mark a genuinely new
alternative to the framework of quantum logic. These ideas are of considerable
interest for the philosophy of quantum mechanics, a claim which I defend with
an extended discussion of their application to our understanding of the
philosophical significance of the no hidden variable theorem of Kochen and
Specker.Comment: Presented to the 2007 conference, New Directions in the Foundations
of Physic
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